Mismatched ants show size doesn't matter to friends

Designing your utopian ant farm? Be sure to stock it with different-sized beasties to help them get along.

Fern-dwelling ants can vary tremendously in size, as shown by the happy couple pictured&colon; the huge (by ant standards), 3-millimetre-long Polyrhachis worker dwarfs the 0.7-millimetre Pheidole worker visible near its front left foot.

And size matters in the ant world. Tom Fayle of Imperial College London and colleagues studied colonies living high up in the rainforest canopy in Borneo and found that ants of similar stature tended not to be seen together.

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When the researchers orchestrated fern invasions by ants of different sizes in the lab, they found that the resident ants tended to repulse interlopers of the same size as themselves, even throwing them off the edge of the fern. But markedly smaller or bigger ants were left to make themselves at home.

This is probably because ants of similar sizes compete for the same resources, such as food or nesting places.